1. Field of the Invention
This invention is concerned with mechanical tools, and in particular with hole drills.
2. Description of the Related Art
It is often desirable to align a hand drill so that holes can be drilled at a specific angle, perpendicular for example, with respect to a surface of a workpiece. Mechanical devices for accomplishing such alignment are commercially available but suffer from major drawbacks.
For example, the PORTALIGN device (Portalign Tool Company, San Diego, Calif.) is made of metal and utilizes an adapter spindle having a shaft that is threaded on one end and has a threaded hole on the other end. To install this device, the drill bit chuck is removed from the drill, the threaded hole on the adapter spindle shaft is screwed onto the threaded shaft of the drill, and the chuck is screwed onto the threaded end of the adapter spindle shaft. The adapter spindle is connected to the shaft via a bushing so that the spindle remains stationary when the shaft rotates. The adapter spindle has two arms about two inches long that are perpendicular to the shaft and have holes parallel with the shaft on their ends. Metal rods that serve as guides slip fit through the holes in the adapter spindle and in a base ring, which has a bottom surface that is flat and perpendicular to the guide holes. The base ring has thumb screws (in threaded holes) that are tightened against the guide rods to lock them in a given position. For drilling holes perpendicular to a workpiece, the bottom surface of the base ring is pressed against the surface of the workpiece with the guide rods locked in place so as to not protrude past the base ring bottom. For drilling holes at an angle to the workpiece, the guide rods are locked so as to protrude beyond the base ring bottom, and the two guide rods and an edge of the base ring are pressed against the workpiece surface.
The PORTALIGN device is inconvenient to use and has significant limitations. The overall length of the drill is increased by the length of the adapter spindle (about 4 inches), which has to be removed when access to the workpiece is limited (by an opposing structure, for example). Removal of the adapter spindle requires a significant amount of time, as well as tools to clamp and turn the chuck and to prevent the drill shaft from turning. In addition, the PORTALIGN device cannot be used to drill holes near an obstruction or sidewall (in a corner, for example) because of the space required for the base ring. Furthermore, both of the operator""s hands are required for the drilling operation, one to hold the drill and the other to hold the PORTALIGN base ring against the workpiece surface. Also, the guide rods need to be lubricated and protected from corrosion so that they will move freely through the guide holes in the adapter spindle.
A simple approach to drilling holes perpendicular to a workpiece is to use a drill bit guide comprised of a cylinder having a concentric hole slightly larger than the drill bit diameter. In this case, one end of the cylinder has a flat surface perpendicular to the cylinder axis that is pressed against the workpiece. Such a drill bit guide requires a separate tool (which may be an insert) for each drill bit size. For drilling holes at other angles, separate tools would be required for all combinations of angles and hole diameters. As with the PORTALIGN device, a drill bit guide must also be held against the workpiece during the drilling operation and has a finite diameter that limits the conditions of use.
Optical devices involving a focused light source and a means for detecting light reflected from the workpiece surface could also be used for drill alignment. In this case, the light source and detector would be arranged so that a maximum in the intensity of the reflected light would occur when the drill bit was at the desired angle. This approach is unnecessarily complicated and would not work well for workpiece surfaces with low reflectance. The light source and the detector would have to be located in very close proximity or a relatively sophisticated electronic system would be required to compensate for the difference in their locations. Alignment between the light source and detector would be critical and difficult to maintain. The most significant disadvantage of this approach, however, is the electronic feedback provided for attaining alignment. Visual readout of the information (via a digital display, for example) would detract attention of the operator from the workpiece, and audio readout would be inaccurate.
The present invention is a device and method for aligning a hand tool so that holes, slots or grooves can be drilled or cut at a desired angle to the surface of a workpiece. Essentially, a device for projecting an image is attached to the hand tool whose orientation is adjusted until no distortion of an image projected onto an area of the workpiece surface is observed This invention is particularly useful for drilling holes at a desired angle and is described with respect to this embodiment.
The device of this invention comprises a light source and a template that are attached to the drill and positioned so as to produce a beam of light that projects an image onto an area of the workpiece surface. The light source and template may be attached to the drill separately but are preferably contained and constrained within a projector housing, which is attached to the drill. An incandescent bulb is preferred but a variety of other light sources could be used, including a in fluorescent light, a laser or a light emitting diode (LED). Power for the light source may be provided by an electrical storage battery or by an alternating current source. The template may be a layer of transparent or translucent glass or plastic material with an image pattern applied by scribing, drilling, cutting, etching, printing, stenciling, stamping, molding or other means, and combinations thereof. The image itself, or improved contrast thereof, may be provided by a pigment or ink. Alternatively, the template may be an opaque material with the image defined by cutout areas. The device may include a curved reflector behind the light source to intensify and/or collimate or focus the light beam used to project the image. The device may also include a lens or lens system to focus the image on the workpiece surface or to adjust the size of the image for optimum sensitivity to the drill orientation. For example, the size of the image may be enlarged for ease of viewing or be reduced to avoid workpiece surface irregularities or adjacent interfering obstructions. Preferably, the light source and template, a reflector, a storage battery and any lenses employed are contained in a plastic or metallic cylindrical projector housing. A suitable projector device is a battery-powered flashlight with a template added for projecting an image. In the simplest embodiment, part of the projector housing serves as the template and a separate template is not required.
The projector device may be attached to the drill by any means providing the rigidity needed to maintain the required orientation with respect to the drill. A preferred attachment means is an open cylindrical clamp (metallic or plastic) that holds a cylindrical projector via spring action and has a flat base that is screwed to the drill. A piece of relatively soft material, such as rubber, may be interposed between the drill and the clamp or between the clamp and the projector to dampen vibrations produced when the drill is operating. For drilling holes perpendicular to the workpiece surface, the device is attached to the drill so that the direction of the projected beam is parallel with the axis of the drill bit. The projector device may be attached to the drill via a pivot with a locking device (a set screw, for example) that allows the angle of the projected beam to be adjusted relative to the drill bit so that the device can be used to drill holes at angles other than 90xc2x0 to the workpiece surface. The pivot assembly may include a reference mark and calibration marks to allow the device to be readily adjusted for a specific drill bit angle.
The method of the present invention involves adjusting the orientation of the drill until the image projected by the projector device of the invention (attached to the drill) is visually observed to exhibit substantially no elongation associated with impingement of the light beam at an oblique angle to the workpiece surface. For drilling holes perpendicular to the surface, the projector device is attached to the drill so that the direction of the projected light beam is parallel to the axis of the drill bit. For drilling holes at other angles relative to the perpendicular, the projector device is positioned so that the projected light beam is coplanar and at the desired angle with respect to the drill bit.
The present invention has significant advantages compared to prior art devices and methods. The device is simple, easily attached (and detached) and easy to use. It also does not increase the overall length of the drill and can be used for drilling holes near sidewalls or other obstructions. Since the projector device is rigidly attached to the drill, both of the operator""s hands can be used for the drilling operation itself, which improves safety. In addition, good accuracy and reduced costs are attained by detecting alignment via the combination of the human eye and brain, which are very sensitive to image distortion, particularly when the image is comprised of regular geometric patterns. In addition, the image is projected on the workpiece and the process of attaining and maintaining alignment is intuitive so that operator attention is not significantly diverted from the drilling operation, which is a significant safety benefit.
Further features and advantages of the invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings.